Embodiments of the present invention relate to a pad conditioner for conditioning chemical-mechanical polishing pads.
Chemical-mechanical planarization (CMP) is used to smooth the surface topography of a substrate, in the manufacture of the integrated circuits and displays, for subsequent etching and deposition processes. A typical CMP apparatus comprises a polishing head that oscillates and presses a substrate against a polishing pad while an abrasive particle slurry is supplied therebetween to polish the substrate. CMP can be used to form a planar surface on dielectric layers, deep or shallow trenches filled with polysilicon or silicon oxide, metal films, and other layers. It is believed that CMP polishing typically occurs as a result of both chemical and mechanical effects, for example, a chemically altered layer is repeatedly formed at the surface of the material being polished and then polished away. For instance, in metal polishing, a metal oxide layer is formed and removed repeatedly from the surface of the metal layer being polished.
During CMP processes, the polishing pad 20 is periodically conditioned by a pad conditioner 24. After the polishing of a number of substrates, the polishing pad 20 becomes glazed with a smoother polishing surface resulting from entangled fibers 26, and accumulated or entrapped polishing residue 28 that clog up the spaces 30 between the fibers of the pad 20, as shown illustrated in FIGS. 1A and 1B. The resultant glazed pad 20 does not effectively retain polishing slurry and can result in increased defects and in certain cases can also lead to non-uniform polishing of a substrate. To remedy pad glazing, the pad 20 is periodically conditioned by a pad conditioner 24 having a conditioning face 32 with abrasive particles 34, such as diamond particles, which is pressed against the used polishing surface 38 of the polishing pad 20, as shown in FIG. 2. The pad conditioner 24 is mounted on an arm 36 that oscillates back and forth as shown by the second position of the dotted arm 36a, while the conditioner 24 is rotated against the pad surface to condition the pad 20 by removing polishing debris, un-clogging pores and fibers on the polishing surface 38, and sometimes also forming micro-scratches that retain polishing slurry. The pad conditioning process can be carried out during a polishing process—known as in-situ conditioning—or outside of a wafer polishing process known as ex-situ conditioning.
Conventional pad conditioners 24 can be covered with a continuous layer, or pattern strips, of abrasive particles 34. For example, FIG. 3A shows a pad conditioner 24 in which the abrasive particles cover its entire conditioning face 32. A circular strip 40 of abrasive particles along the periphery of the conditioning pad has also been used as shown in FIG. 3B. The circular strip 40 can also be broken into segments 40a,b with alternating bands of abrasive particles and smooth regions, as shown in FIG. 3C. In yet another configuration, wedges 42 of abrasive particles 24 are spaced apart from one another and extend tangentially across the conditioning face 32 as shown in FIG. 3D. The abrasive particle patterns can be used to limit the quantity of the diamond bonded area which could limit costs. However, some of these patterns often result in non-uniform and inconsistent pad conditioning effects that can vary across the pad surface. The patterned abrasive pad configurations can also cause slurry to be forced into and entrapped within particular regions of the pad conditioner 24, further reducing the uniformity of pad conditioning.
Conventional pad conditioners 24 can also result in splashing and dried slurry accumulation when they pick-up polishing slurry from the polishing pad surface 38 and randomly expel the slurry from the edges of the pad conditioner 24. For example, as shown in FIG. 2, centrifugal forces generated by the rotating pad conditioner 24 cause the slurry picked-up by the pad conditioner 24 to be ejected along the edges of the pad conditioner as shown by the arrows 44. Slurry depletion from surface of the polishing pad 20 caused by the pad conditioner 24 can cause dry spots on the polishing pad surface, and can result in increased particle defect counts and gross/micro scratching defects.
Accordingly, it is desirable to have a pad conditioner with a conditioning face that provides uniform and repeatable conditioning of polishing pads. It is also desirable to condition a polishing pad without excessive loss of polishing slurry during the conditioning process. It is further desirable to have a pad conditioner with a dispersion of abrasive particles that provides optimal conditioning while controlling the amount of abrasive particles used on the conditioning face.